In the case of differential input mode serial communication such as controller area network (CAN) communication, recommended standard (RS)-485 communication, recommended standard (RS)-422 communication, or the like, a terminating resistance needs to be installed at a termination of a communication device.
FIG. 1 is a diagram illustrating a differential input mode communication device in the related art. Since the communication device has impedance according to various design references in the differential input mode communication, a reflection phenomenon occurs at the termination of the communication device.
As a result, resistances 12 and 13 are connected to both terminations of a line 11 of the communication device to circulate constant current throughout the line, to reduce the reflection phenomenon and be resistant to noise by adjusting impedance on the line 11. In this case, installed resistances are terminating resistances 12 and 13.
FIGS. 2 and 3 are diagrams illustrating examples of installing terminating resistances in the differential input mode communication device in the related art.
In the differential input mode communication device in the related art, terminating resistances are inserted by using a method of installing terminating resistances 23 and 24 on communication boards 21 and 22 positioned at terminations as illustrated in FIG. 2 or installing terminating resistances 35 and 36 on outer communication connectors 33 and 34 of communication boards 31 and 32 positioned at terminations as illustrated in FIG. 3.
However, since the differential input mode communication device in the related art needs to manage the communication board so as to distinguish whether the communication board is positioned at the termination, it is inconvenient to maintain and manage the communication device and when the communication device is first installed, a mistake in which the terminating resistance is removed from the communication board positioned at the termination may occur.